On the other hand, permanent virtual circuits are preconfigured into the network.

Logical channel identifiers remain assigned to a virtual circuit for the duration of the connection.

The maximal length may be different at the two ends of the virtual circuit.

Examples of transport layer protocols that provide a virtual circuit:

Permanent virtual circuits eliminate the need for repeated call set-up and clearing.

Once the channel groups have been established, the individual channels are bonded into a pair of virtual circuits, one in each direction.

While using packet switching, X.25 is built on the concept of virtual circuits emulating traditional telephone connections.

Within any given frequency band, it was possible to have many, many, virtual circuits between devices.

Multiple virtual circuits can be active on the same physical end-points (performed by using subinterfaces).

On digital lines, a virtual circuit can be created to serve either purpose, while sharing a single physical circuit.